Abstract. Acid mine site remediation is a significant problem, both in the U.S and globally. Due to the volume of acid producing rock the only practical solution is minimizing acid production by reducing or eliminating water flow through the rock. Typically, this is achieved through emplacement of a cap over the waste rock. The Ruby Gulch repository at the Gilt Edge Mine NPL Site is such a capped waste rock repository. Eliminating discharge from valley-fill capped waste-rock repositories is difficult and multiple factors can cause continuing oxidation and ARD discharge. Consequently, early in the cap-cover design EPA and the Bureau of Reclamation design-build team recognized the need for a long-term monitoring system which would provide actionable information on the repository performance and behavior. Specifically, the following objectives were defined for a monitoring system: 1) provide information on the integrity and performance of the newly constructed surface cover and diversion system; 2) continuously assess the waste's hydrological and geochemical behavior, such that rational decisions can be made for the operation of this cover and liner system; 3) provide easy and timely information access on system performance to a variety of stakeholders; and 4) generate information and insights which can be used to enhance future cover and monitoring discussions between EPA, the Bureau of Reclamation and DOE Idaho National Laboratory. A longterm monitoring system was designed and integrated into the multi-layered geomembanerock-soil cap-cover over the 65-acre, 450'-high, sulfide waste-rock dump to provide information to meet these objectives. The system consists of tensiometers, lysimeters and thermocouples in four wells, a 523-electrode resistivity system installed below the cap and in the wells, a weather station, and a precision outflow-meter at the toe-discharge of the repository. Continuous data from this system as well as auxiliary manually collected samples are parsed into a web accessible central server. Automated and on demand data processing allows for 2-D, 3-D and 4-D resistivity tomography and user controllable data mining. The philosophy underlying this system is that it should provide both for effective automated and autonomous data collection and for a cost effective way for multiple stakeholders to use this data.
Effective ARD repository management requires ongoing assessment of remedial integrity and operational performance in such a manner that short and long term risks and cost are balanced and optimized. Such management requires actionable information on the behavior of the repository. This information will typically be derived from diverse data (physical, chemical and hydrological), forward and inverse hydrological, geochemical and geophysical models and cost/benefit models. With the increase in volumes of data and complexity of analysis, end users face increasing challenges in obtaining information in a timely and cost effective manner. A web accessible workflow environment for performance monitoring, designed at the Idaho National Laboratory (INL), was implemented for a capped ARD repository (the Ruby Gulch Repository) and is part of the Gilt Edge Superfund site in South Dakota. This repository is instrumented with a geophysical, hydrological and environmental sensor network. Data from this network are transmitted automatically every two hours to a server. At the server, the data are automatically parsed in a relational database and analyzed using automatically executing scripts. The resulting information is both transmitted through automated reports and accessible by users through a web application. The combination of near real time reporting and analysis and integration with analysis tools provides for actionable information on short and long term repository behavior. The structure of a web accessible workflow system for performance monitoring is well suited for both managing data, creating information and providing access to information for diverse users.
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